1. Field of the Invention
The present invention relates to a method for controlling the temperature when growing an epitaxial layer on a substrate by using an epitaxial growth apparatus.
2. Description of the Related Art
There has been disclosed a wafer handling method which heats the inside of the treatment chamber of an epitaxial growth apparatus by heating means, conveys a substrate into the heated treatment chamber, and controls heating by heating means so that the temperature difference between the surface and the back of the substrate is decreased in order to prevent the warpage of the substrate while the substrate is conveyed (for example, refer to Patent Document 1). In this method, the heating means is a halogen lamp arranged to the upside and downside of the treatment chamber and surface temperatures of the substrate heated by the halogen lamp and a susceptor for supporting the substrate in the treatment chamber are measured by a pyrometer. Specifically, the pyrometer is constituted so as to measure surface temperatures of the substrate and susceptor in the treatment chamber by receiving thermal emission energy from the substrate and susceptor. Moreover, in order to convey the substrate to the treatment chamber, a conveying robot and lift mechanism are used.
In the case of the wafer handling method thus constituted, the halogen lamp is controlled based on a detection output of the pyrometer, that is, heating by the halogen lamp is controlled so that the temperature difference between the surface and the back of the substrate is decreased during conveyance. Therefore, when conveying the substrate to the treatment chamber, it is possible to prevent the warpage generated in the substrate supported by the conveying robot and lift mechanism.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2000-269137 (claim 4, Paragraphs [0016] to [0022], [0037], FIG. 1)
However, in the case of the conventional wafer handling method shown in Patent Document 1, a pyrometer serving as a radiation thermometer is used. Because of the characteristics of the radiation thermometer, that is, because temperature is calculated by using infrared energy and emissivity to be fluctuated due to an external factor, indirectly measured temperature by the radiation thermometer is changed with time and shifted from actual substrate temperature. Therefore, it has been necessary to regularly directly measure the substrate temperature in the treatment chamber by using a susceptor having a thermocouple and calibrate the radiation thermometer. Because the calibration of the radiation thermometer requires substantial time (two to three days), there have been problems that it is impossible to calibrate the radiation thermometer after epitaxial growth treatment every time and that it is impossible to grow an epitaxial layer on a mass-production substrate while the radiation thermometer is calibrated. Therefore, at the time of regular maintenance once for two years or when extremely abnormal quality of a mass-production substrate on which an epitaxial layer is grown occurs, only confirmation of temperature and calibration of the radiation thermometer are performed. Therefore, frequencies of these operations are lowered and it is impossible to monitor the shift of indirectly measured temperature from actual substrate temperature by the radiation thermometer. Therefore, there has been a problem that the quality of the mass-production substrate on which an epitaxial layer is grown is gradually deteriorated.
Moreover, in the case of the above conventional wafer handling method shown in Patent Document 1, the substrate temperature in the treatment chamber is indirectly measured by a radiation thermometer through transparent top and bottom walls made of quartz. Therefore, when the transparent top and bottom walls are contaminated, the indirectly measured temperature by the radiation thermometer is shifted from an actual substrate temperature and there has been a problem that the quality of the epitaxial substrate is deteriorated.